Shaft fitted rotatably in the casing of a pressure chamber

ABSTRACT

The support of a shaft (7) which is rotatably supported in through-holes of the housing (1) of a pressure chamber in bushes (11, 12) provided with sealing rings and which is secured against axial displacement by securing rings (21, 22) is to be improved in such a way that a low-wear and secure arrangement of the shaft (7) and bearing bushes (11, 12) is achieved. For this purpose, it is suggested that each through-hole (9, 10) of the housing (1) comprise a collar (15, 16) which projects radially inward and forms a support for a projection which is directed radially outward and with which each bush (11, 12) is provided, the front side (19, 20) of the latter facing the pressure chamber simultaneously forming a support for a securing ring (21, 22) arranged on the shaft (7), wherein the two bearing sides of the shaft (7) have the same diameter.

The invention is directed to a shaft which is rotatably supported inthrough-holes of the housing of a pressure chamber in bushes and securedagainst axial displacement by securing rings, as well as to sealingrings between the bearing side of the shaft and the bush on one side andbetween the bush and the housing on the other side.

Bushes can be provided for the rotatable support of a shaft in a housingwhich are guided through the wall of the housing and supported on thewall. The bush is recessed into the wall of the housing and can also bescrewed, wedged or pinned to the wall in addition. Every bush has anexternal annular flange by means of which the bush is supported on thewall in the axial direction of the shaft from the outside, that is fromthe side of the wall of the housing remote of the pressure chamber. Asecuring ring which is placed from the outside on each end of the shaftprojecting out of the bushes forms the closure and is supported on theoutside end faces of the bushes. The axial position of the rotatableshaft within the housing is fixed by means of this arrangement. Thesecuring rings accordingly fix the shaft in its position in relation tothe housing so that the shaft can not wander out or be pulled or pushedout of the housing in either axial direction (DE-OS No. 34 43 302).

Although the known arrangement has the advantage that it can be mountedin a simple manner, it nevertheless has a number of disadvantages:

the securing rings can wear easily because the end faces of the bushesfacing the pressure chamber are constantly acted upon by pressure;

due to the application of pressure on the bushes, the shaft, in turn, isconstantly acted upon by tensile force via the securing rings;

when a securing ring breaks, the respective bearing bush also loses itssecure support. If the pressure force acting on the front annularsurface of the bush exceeds the force by which the bush is held in thehousing, the latter can be suddenly detached and thrown out in themanner of a projectile;

the securing rings are constantly loaded and therefore generate highfriction.

Based on these disadvantages the object of the present invention is toimprove the known support of the rotatable shaft in the housing of thepressure chamber in such a way that a wear-resistant and securearrangement of the shaft and bearing bushes is achieved.

This object is met in that every through-hole of the housing comprises acollar which projects radially inward and forms a support for aprojection which is directed radially outward and with which every bushis provided, and the front side of the latter facing the pressurechamber simultaneously forms a support for a securing ring arranged onthe shaft, wherein the two bearing sides of the shaft have the samediameter. The shaft is accordingly relieved of tension and the bearingbushes can not be propelled out by the internal pressure of the housing.The securing rings are likewise relieved of tension so that there is nolonger any frictional wear. The equivalence in diameter of the bearingsides ensures that no axial force is applied via the shaft itself.

The invention is described in more detail in the following withreference to an embodiment example:

FIG. 1 shows a cross section through a pressure cylinder. Such cylinderscomprise two pistons which are movable in opposite directions, eachpiston comprising a toothed rack meshing with the pinion of therotatable shaft and accordingly rotating the shaft when moved.

The housing 1 of the pressure cylinder encloses the cylindrical pressurechamber 2 which extends vertically in end-to-end length with respect tothe drawing plane of the figure. The pressure chamber 2 is filled with apressure medium, e.g. compressed air or hydraulic fluid, via aconnection 3. The pressure medium is removed from the pressure chamber 2via a connection 4 which opens into an axial bore hole 5. The inlet andoutlet of the pressure medium is controlled e.g. via valves and/orslides (not shown) which are arranged outside the housing 1 andcommunicate with the connections 3 and 4 in a conventional manner vialine connections (not shown).

A piston, for example, (not shown) is guided in the cylindrical pressurechamber 2 so as to be longitudinally movable vertically with respect tothe drawing plane in the figure. The movement of the piston is caused bythe pressure medium which can flow in and out via the connections 3 and4. The pistons move in one or the other axial direction, i.e. verticallyin relation to the drawing plane of the figure, depending on theconnection 3 or 4 through which the pressure medium flows in or out.

Each piston is provided with a toothed rack, in a manner known per se,which engages in the gear tooth pinion 6 of the shaft 7 which isrotatably supported in the housing 1. The pistons accordingly transmittheir respective longitudinal movement inside the pressure chamber 2 tothe rotatable shaft 7 and cause the shaft 7 to execute a correspondingrotating movement in the direction of the curved double arrow 8. Themagnitude of this rotating movement 8 can range from a few angulardegrees to several complete revolutions. The piston and toothed rack canthus be moved in opposite directions.

The rotatable shaft 7 is rotatably supported in opposite through-holes 9and 10 of the housing 1 in bushes 11 and 12 and has the same diameter onboth bearing sides. Each of the through-holes 9 and 10 comprises acollar 15 and 16 projecting radially inward on the side 13 and 14 of thehousing 1 remote of the pressure chamber 2, which collar 15 and 16 formsa support for an annular flange 17 and 18 with which every bush 11 and12 is provided. The bushes 11 and 12 are pressed against the collars 15and 16 of the two through-holes 9 and 10 by their annular flanges 17 and18 under the pressure force of the pressure medium in the pressurechamber 2 acting on the inside end face 19 and 20 of the bushes 11 and12 facing the pressure chamber 2 and are securely held by the collars 15and 16.

The end faces 19 and 20 also serve simultaneously as a support forsecuring rings 21 and 22 which define the bearing seats 23 and 24 towardthe shank 25 of the rotatable shaft 7 and are recessed into therotatable shaft 7. As can also be seen from the drawing, the twosecuring rings 21 and 22 prevent the rotatable shaft 7 from wanderingout of the housing 1 in the axial direction 33 but are not axiallyloaded so that only slight friction occurs in this location during arotating movement of the shaft.

Assuming that the pressure chamber 2 is opened, e.g. by a cover (notshown), in a plane not situated in the drawing plane of the figure butparallel thereto, the rotatable shaft is mounted in the housing 1approximately as follows:

The bush is first inserted into the through-hole 10. The shaft 7 is theninserted into the pressure chamber 2 through the free through-hole 9and, with the securing ring 22 slid loosely on the shank 25 up to thepinion 6, pushed through the bush 12 along the free length of the shank25. The second bush 11 is then inserted into the through-hole 9. Thelower end 27 of the shaft 7 is then threaded into the inner bore hole 26until the previously inserted securing ring 21 abuts at the end face 20.The other securing ring 22 is then slipped back over the shank 25 andlocked into the groove (not shown) of the shank 25 provided for thispurpose in front of the front side 19 of the bush 12.

For the sake of completeness, it is noted that O-seals 28 are providedbetween the bushes 11 and 12 for sealing the through-holes 9 and 10.Similarly, O-seals 29 are arranged between the shaft 7 and the bushes 11and 12 for sealing the bearing seats 23 and 24. The upper end 30 of theshaft 7 ends in a projecting pin 31, whereas a recess 32 is formed inthe lower end 27 which can be provided with key faces.

List of Reference Numbers

1 housing

2 cylindrical pressure chamber

3 connection

4 connection

5 axial bore hole

6 gear tooth pinion

7 rotatable shaft

8 rotating movement

9 through-hole

10 through-hole

11 bush

12 bush

13 side remote of the pressure chamber

14 side remote of the pressure chamber

15 collar projecting radially inward

16 collar projecting radially inward

17 annular flange

18 annular flange

19 inside end face

20 inside end face

21 securing ring

22 securing ring

23 bearing seat

24 bearing seat

25 shank

26 inner bore hole

27 lower end

28 O-seal

29 O-seal

30 upper end

31 projecting pin

32 recess

33 axial direction

What is claimed is:
 1. An assembly, comprising:a one-piece housingdefining a pressure chamber and having axially opposite through-bores,wherein a housing wall portion, which defines each of saidthrough-bores, has a radially inwardly projecting collar; bearing busheslocated in said through-bores, respectively, and having each a radiallyoutwardly directed projection, which rests against a respective collarunder pressure generated in said pressure chamber and acting on an endsurface of said projection facing said pressure chamber; a rotatabletooth gear shaft located in said pressure chamber and having a toothedgear and opposite bearing shank portions of an equal diameter, whichextend from opposite side surfaces of said toothed gear and which aresupported in said bearing bushes; sealing rings arranged, respectively,between said bearing bushes and housing walls, which define saidthrough-bores, and between said bearing shank portions and said bearingbushes; and securing rings for retaining said toothed gear shaft againstaxial displacement, wherein said securing rings rest against respectiveend surfaces of respective projections of said bearing bushes.
 2. Theassembly of claim 1, wherein said projection is formed as an annularflange of a respective bearing bush.